1. Field of the Invention
The present invention relates to a tilt device for a marine propulsion unit.
2. Description of the Related Art
Conventionally, as a tilt device for a marine propulsion unit, there has been suggested a trim-tilt device for a marine propulsion unit comprising a cylinder device interposed between a boat body and a marine propulsion unit. It is tiltably supported with respect to the boat body and a hydraulic fluid supply/discharge device for extending and contracting the cylinder device and tilt operating the a marine propulsion unit by controlling supply and discharge of the hydraulic fluid to the cylinder device. The hydraulic fluid supply/discharge device comprises a motor, a pump, a tank and a flowing passage with a switching valve.
There is a conventional art such that an armored case of a motor made from resin is used as a substitute for an armored case made of deep-draw mold iron intending to reduce the production cost of the motor and improve corrosive resistance.
However, the conventional art using a resin made armored case of the motor involves the following problems.
(1) Since seawater or the like submerges a motor of the marine propulsion unit, the motor has a water-resistant airtight construction. Therefore, if an armored case of the motor is made of resin, the resin made case having low heat conductivity acts as a heat-retaining member, so that hot air is easily accumulated in the interior of the motor.
(2) According to (1), the interior of the motor reaches a high temperature. As a result, a winding wire of an armature is bum out and an abnormal friction of a brush or the like occurs, so that the durability and the life of the motor are shorten.
The object of the invention is to prevent heat accumulation in the inside of a resin made motor composing a tilt device for a marine propulsion unit and to improve the durability and the life of the motor.
The present invention provides a tilt device for a marine propulsion unit comprising a cylinder device interposed between a boat body and a marine propulsion unit, which is tiltably supported with respect to the boat body. It also has a hydraulic fluid supply/discharge device for extending and contracting the cylinder device and tilt operating a marine propulsion unit by controlling the supply and discharge of the hydraulic fluid to the cylinder device. The hydraulic fluid supply/discharge device comprises a motor, a pump, a tank and a flowing passage with a switching valve. An armored case of the motor is made of resin and a circulating passage of the hydraulic fluid to be circulated by the pump is arranged in the inside of the motor.